1. Field of the Invention
The present invention is directed to an x-ray diagnostics installation, and in particular to such an installation having means for monitoring the average image brightness on the output luminescent screen of the x-ray image intensifier, and controlling the operation of the x-ray tube based thereon.
2. Description of the Prior Art
An x-ray diagnostics installation is disclosed in European Application 0 217 456 which includes a detector for the average image brightness of the output luminescent screen of the x-ray image intensifier in a predetermined region of the screen. The detector is a semiconductor surface on which the entire output image of the x-ray image intensifier output screen can be imaged, and includes means for selecting a predetermined region of the semiconductor surface for use in generating the control signal. The detector consists of an array of a plurality of individual detector elements, the outputs of the individual elements being combined to form a brightness signal for the selected measuring field An output amplifier must be provided for each detector element, which requires a considerable circuit outlay, and reduces the resolution obtainable by the array because of the physical space which must be occupied by each amplifier, thereby limiting the number of detector elements which can be provided in a given area.